Controlling voice communications over a data network

ABSTRACT

A method and apparatus of communicating over a data network includes providing a user interface in a control system for call control and to display information relating to a call session. The control system communicates one or more control messages (e.g., Session Initiation Protocol or SIP messages) over the data network to establish a call session with a remote device in response to receipt of a request through the user interface. One or more commands are transmitted to a voice device associated with the control system to establish the call session between the voice device and the remote device over the data network. A Real-Time Protocol (RTP) link may be established between the voice device and the remote device.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. Ser. No. 09/524,342, filed Mar. 13, 2000,which is hereby incorporated by reference.

BACKGROUND

The invention relates to controlling voice communications over a datanetwork.

Data networks are widely used to link various types of network elements,such as personal computers, servers, gateways, network telephones, andso forth. Data networks may include private networks (such a local areanetworks or wide area networks) and public networks (such as theInternet). Popular forms of communications between network elementsacross such data networks include electronic mail, file transfer, webbrowsing, and other exchanges of digital data.

With the increased capacity and reliability of data networks, voicecommunications (including telephone calls, video conferencing, and soforth) over data networks have become possible. Voice communicationsover data networks are unlike voice communications in a conventionalpublic switched telephone network (PSTN), which provides users withdedicated, end-to-end circuit connections for the duration of each call.Communications over data networks, such as IP (Internet Protocol)networks, are performed using packets or datagrams that are sent inbursts from a source to one or more destination nodes. Voice data sentover a data network typically shares network bandwidth with conventionalnon-voice data (e.g., data associated with electronic mail, filetransfer, web access, and other traffic).

Various standards have been proposed for voice and multimediacommunications over data networks. One such standard is the H.323Recommendation from the International Telecommunications Union (ITU),which describes terminals, equipment, and services for multimediacommunications over data networks.

Another standard for voice and multimedia communications is the SessionInitiation Protocol (SIP), which establishes, maintains, and terminatesmultimedia sessions over a data network. SIP is part of a multimediadata and control architecture developed by the Internet Engineering TaskForce (IETF). The IETF multimedia data and control architecture alsoincludes the Resource Reservation Protocol (RSVP) for reserving networkresources; the Real-Time Transport Protocol (RTP) for transportingreal-time data and providing quality of service (QoS) feedback; theReal-Time Streaming Protocol (RTSP) for controlling delivery ofstreaming media; the Session Announcement Protocol (SAP) for advertisingmultimedia sessions by multicast; and the Session Description Protocol(SDP) for describing multimedia sessions.

To perform voice communications over a data network, a typical computersystem (such as a desktop computer system or a portable computer system)may be equipped with voice processing capabilities. Such capabilitiesinclude a microphone, ear phones or speakers, and speech processingsoftware. Typically, the speech processing software includescoder/decoders (CODECs) to encode and decode voice data. The voiceprocessing software, including the CODECs, may be run on amicroprocessor of a typical computer system. However, due to theintensive data processing typically required to process voice data,speech performance may not be optimum. For example, there may be delaysassociated with the transfer of such voice data due to the amount oftime needed to process the voice data. Also, if certain types of CODECsthat have less resource requirements are selected, voice quality maysuffer.

Also, the computer system needs to be fitted with speakers, microphones,and sound cards to enable speech processing. Further, such speakers,microphones, and sound cards may not provide the desired level ofquality, or if they do, may be relatively expensive. Additionally, toadd such speech processing components to a computer system may requiresome configuration to be performed by a user, a process that anunsophisticated user may have difficulty with.

Unless a computer system with powerful processing capabilities areprovided, the voice quality provided by such computer systems are not atthe level typically experienced (and expected) by users of standardtelephones. Such “standard” telephones may include analog telephonescoupled to a local or central switching office or digital telephonescoupled to a private branch exchange (PBX) system. More recently,network telephones have been developed that are capable of beingconnected directly to a data network, such as an IP network. Thesenetwork telephones are capable of placing telephony calls over a datanetwork. The voice quality offered by such telephones are typicallysuperior to those that can be offered by computer systems, since suchnetwork telephones typically include dedicated digital signal processors(DSPs) that perform the data intensive calculations involved in speechprocessing. However, the existing network telephones do not providedesired multimedia presentation capabilities such as those offered bydisplays of computer systems. Thus, while network telephones offersuperior speech capabilities, it does have the desired multimediacapabilities. On the other hand, computer systems have superiormultimedia capabilities, but they suffer from relatively poor speechprocessing performance.

A need thus exists for an improved method and apparatus for controllingvoice communications over data networks.

SUMMARY

In general, according to one embodiment, a method of communicating overa data network includes communicating, in a control system, one or morecontrol messages over the data network to establish a call session witha remote device coupled to the data network. One or more controlcommands are transmitted to a telephony device coupled to the datanetwork to establish the call session between the telephony device andthe remote device over the data network. Information associated with thecall session is displayed on the control system.

In general, according to another embodiment, a system includes a userinterface having one or more selections for call control relating tocall sessions. A controller receives a request from the user interfaceand generates one or more messages for communicating over a data networkto establish a call session with a remote device. An interface transmitsone or more commands relating to the call session to a user terminal toestablish a link between the user terminal and the remote device overthe data network.

Some embodiments of the invention may include one or more of thefollowing advantages. The voice processing capabilities of a voicedevice, such as a network telephone, may be advantageously used toprovide superior voice quality, while at the same time, a control systemsuch as a computer may be used to provide a convenient user interfacefor the user to perform call control and to view status and otherinformation relating to the call session. Thus, voice quality associatedwith call sessions over data networks such as packet-switched datanetworks is enhanced using embodiments of the invention.

Other features and advantages will become apparent from the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is block diagram of an embodiment of a communications system.

FIG. 2 illustrates components in a network telephone and a call controlsystem in accordance with an embodiment.

FIG. 3 illustrates control and data paths between network elements usedduring a call session in accordance with one embodiment.

FIGS. 4 and 5 illustrate example screens displayed by the call controlsystem of FIG. 2 in accordance with an embodiment.

FIG. 6 is a message flow diagram of messages exchanged between networkelements in the communications system of FIG. 1 for processing anincoming call.

FIG. 7 is a message flow diagram of messages exchanged between networkelements in the communications system of FIG. 1 for placing an outgoingcall.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details and that numerous variations ormodifications from the described embodiments may be possible. Forexample, although reference is made to Session Initiation Protocol (SIP)communications sessions in accordance with some embodiments, otherprotocols may be performed in further embodiments.

Referring to FIG. 1, a communications system 10 includes a first datanetwork 12 and a second data network 14 that are coupled through a datanetwork cloud 16. The data network cloud 16 may include various links,communications paths, and routers for routing messages between datanetworks 12 and 14. The data network cloud 16 may include a publicnetwork such as the Internet. The data networks 12 and 14 may be privatenetworks such as local area networks (LANs) or wide area networks(WANs). In the ensuing discussion, one or some combination of the datanetworks 12 and 14 and data network cloud 16 may be referred tocollectively as the data network 11. As used here, a “data network” or“network” may refer to one or more communications networks, channels,links, or paths and systems (such as routers) used to route data oversuch networks, channels, links, or paths.

The data network 11 may include an Internet Protocol (IP) network, whichis a packet-switched network. One version of IP is described in Requestfor Comments (RFC) 791, entitled “Internet Protocol,” dated September1981. Other versions of IP, such as IPv6, or other connectionless,packet-switched standards may also be utilized in further embodiments. Aversion of IPv6 is described in RFC 2460, entitled “Internet Protocol,Version 6 (IPv6) Specification,” dated December 1998. Packet-switcheddata networks such as IP networks communicate with packets, datagrams orother units of data over the data networks. Unlike circuit-switchednetworks, which provide a dedicated end-to-end connection or physicalpath for the duration of a call session, a packet-switched network isone in which the same path may be shared by several network elements.Packet-switched networks such as IP networks are based on aconnectionless internetwork layer. Packets or other units of datainjected into a packet-switched data network may travel independentlyover any path (and possibly over different paths) to a destinationpoint. The packets may even arrive out of order. Routing of the packetsis based on one or more addresses carried in each packet.

The packet-based network 12 may also be connection-oriented, such as anATM (Asynchronous Transfer Mode) network or a Frame Relay network. In aconnection-oriented, packet-based network, a virtual circuit orconnection is established between two end points. In suchconnection-oriented networks, packets are received in the same order inwhich they were transmitted.

Network elements connected to the data network 11 may also be coupledthrough a data network-PSTN gateway 20 to a public-switched telephonenetwork (PSTN) 22. The link between the gateway 20 and the PSTN 22 maybe a primary rate interface (PRI) link according to ISDN (IntegratedServices Digital Network). Standard non-data network telephones 24 maybe coupled to the PSTN 22. Call sessions can thus be established betweena data network element and one of telephones 84.

In the example embodiment as illustrated in FIG. 1, audio (e.g., voice)and multimedia (e.g., audio and video) communications may occur over thedata network 11 between or among various network elements, includingnetwork telephones 30 and 34 and call control systems 32 and 36. Otherdevices capable of voice or multimedia sessions include SIP (SessionInitiation Protocol) client systems 38 and 40. The SIP client systems 38and 40 are capable of communicating using SIP messaging to establishcall sessions. As used here, a “call session” refers generally to eithera voice or a multimedia session established between two or more elementscoupled to the data network 11 (or any other packet-switched datanetwork). SIP is part of the multimedia data and control architecturefrom the Internet Engineering Task Force (IETF). A version of SIP isdescribed in RFC 2543, entitled “SIP: Session Initiation Protocol,”dated August 1999. SIP may be used to initiate call sessions as well asto invite members to a session that may have been advertised by someother mechanism, such as electronic mail, news groups, web pages, andother mechanisms. The other protocols in the IETF multimedia and controlarchitecture include the Resource Reservation Protocol (RSVP), asdescribed in RFC 2205; the Real-Time Transport Protocol (RTP), asdescribed in RFC 1889; the Real-Time Streaming Protocol (RTSP), asdescribed in RFC 2326; the Session Description Protocol (SDP), asdescribed in RFC 2327; and the Session Announcement Protocol (SAP).

Other standards may be employed in further embodiments for controllingcall sessions over the data network 11. Such other standards may be anyother standard that provides for interactive, real-time voicecommunications over the data network.

The SIP client systems 38 and 40 as shown in FIG. 1 include clientapplication programs that are capable of sending SIP requests to performcall requests. The systems 38 and 40 may also be SIP servers. A serveraccording to SIP may be an application program that accepts SIP requeststo service calls and to send back responses to SIP requests. Thus, asystem can be either a SIP client or a SIP server. A SIP proxy system,such as system 42, may include an intermediary program that acts as botha server and a client for making requests on behalf of other clients.

In the system 10 as shown in FIG. 1, the call control systems 32 and 36are SIP-enabled; that is, the call control systems 32 and 36 are capableof sending and accepting SIP requests to establish call sessions. Thecall control systems 32 and 36 may be implemented on a standard computersystem platform. Unlike the call control systems 32 and 36, however, thenetwork telephones 30 and 34 are not SIP-enabled in one embodiment.Although they are capable of communicating audio data over the datanetwork 11, the network telephones 30 and 34 are not enabled to send oraccept SIP messages (or other types of messages for establishinginteractive, real-time voice communications) to establish call sessions.In accordance with some embodiments, the establishment, management, andtermination of call sessions are controlled by the call control systems32 and 36. Thus, the call control system 32 makes SIP requests on behalfof the network telephone 30, while the call control system 36 makes SIPrequests on behalf of the network telephone 34. Once a call session isestablished, the network telephone 30 or 34 participates in thecommunication of voice data over the network 11.

By employing the arrangement as shown in FIG. 1, the superior voicecapabilities of network telephones 30 and 34 may be utilized to provideenhanced voice quality for users making telephony calls over the datanetwork 11. At the same time, associated call control systems 32 and 36are used to provide call signaling communications and to provide theuser with a convenient user interface to perform call control as well asdisplay information associated with the call session.

The call control system 32 and the network telephone 30 may becollectively referred to as a telephony system 31. Similarly, the callcontrol system 36 and network telephone 34 may be collectively referredto as a telephony system 33. To establish a call session between thetelephony system 31 or 33 and another SIP-enabled remote system 100, asshown in FIG. 3, the call control system 32 or 36 sends SIP messages tothe remote system 100 to establish a call session. The remote system 100may be any system or device on the data network 11 that is capable ofparticipating in a SIP-established call session. The call control system32 or 36 also exchanges commands according to a predetermined formatwith the network telephone 30 or 34 to let the network telephone 30 or34 know of the current status of the call setup. Once a call isestablished, a link may be established between the network telephone 30or 34 and the remote system 100 over the data network 11. The link maybe a Real-Time Protocol (RTP) link to communicate with voice data. Thus,in the telephony system 31 or 33, the call control system 32 or 36communicates the control signaling to establish a call session, while areal-time link is established directly between the network telephone 30or 34 and the remote system 100 for communicating voice or other typesof audio data. In one embodiment, the call control messaging between thecall control system and remote system, the control messaging between thecall control system and the network telephone, and the call sessionbetween the network telephone and the remote system all occur over thedata network 11.

The call control system 32 or 36 is also equipped with speech processingelements to allow it to communicate voice data with other devices on thedata network 11. Thus, a user at the call control system 32 or 36 mayselect whether to use the call control system or the network telephoneas the terminal device in the established call session. In addition, ifthe call control system 32 or 36 is powered off, the network telephone30 or 34 may be used as a stand-alone device to communicate voice incall sessions over the data network 11.

Referring to FIG. 2, the components in the network telephone 30 or 34and in the call control system 32 or 36 are illustrated in greaterdetail. The network telephone 30 or 34 includes a network interface 102that is coupled to the data network 11. Above the network interface 102are several software layers, including a device driver layer 104, aTCP/IP or UDP/IP stack 106, and an RTP layer 108. TCP is described inRFC 793, entitled “Transmission Control Protocol,” dated September 1981;and UDP is described in RFC 768, entitled “User Datagram Protocol,”dated August 1980. TCP and UDP are transport layers for managingconnections between network elements over an IP network. Packetsreceived by the network interface 102 are passed up through the severallayers 104, 106 and 108. Control packets are transmitted by the TCP/IPor UDP/IP stack 106 to one or more control tasks 110 in the networktelephone 30 or 34. The one or more control tasks 110 may be implementedas software routines executable on a control unit 112. Instructions anddata associated with the control tasks 110 may be stored in a storagedevice 114. The control tasks 110 are responsible for generation ofcontrol signaling as well as exchanging commands and responses with itsassociated call control system 32 or 36 over the data network 11.

Voice data may be passed through the RTP layer 108 to a speechprocessing application 116, which may also be executable on the controlunit 112. For faster processing of voice data, a digital signalprocessor (DSP) 118 is included in the network telephone 30 or 34 toprovide data intensive signal processing tasks. For example, thecoder/encoder (CODEC) may be implemented in the DSP 118. The networktelephone may also include a display screen to display text dataassociated with a call session. The size of the display screen 120 maybe limited so that only limited amounts of text data may be displayed inthe display screen 120. The network telephone also includes numeralsbuttons that may be controlled by button control circuitry 122. Thebuttons may include numeric buttons, speed dial buttons, a transferbutton, a hold button, a redial button, and other telephony buttons.Activation of any one of the buttons may cause generation of some typeof an indication (such as an interrupt) that is forwarded to the controltasks 110.

The call control system 32 or 36 also includes a network interface 150.Above the network interface 150 are several layers, including a devicedriver layer 152, a TCP/IP or UDP/IP stack 154, a SIP stack 156, and anRTP layer 158. The SIP stack 156 is responsible for processing orgenerating SIP requests and responses communicated over the data network11. The SIP stack 156 is in communication with one or more control tasks160 in the call control system 32 or 36. The SIP stack 156 is generallya state machine that provides parsing, processing, and generation of SIPrequests and responses.

The call control tasks 160 are responsible for generating controlsignaling to establish call sessions over the data network 11 as well asto respond to received control signaling. In addition, the control tasks160 are responsible for exchanging commands and responses with thenetwork telephone 30 or 34 to establish such call sessions. The callcontrol system 32 or 36 may also include one or more graphical userinterface (GUI) routines 162 that control the presentation ofinformation (text or graphical) on a display 164 of the call controlsystem. Further, the user interface provided by the GUI routines 162 mayinclude selectors for call control and indicators of the status of acall session.

In the illustrated arrangement, the RTP layer 158 sends audio data to,or receives audio data from, a CODEC 166. The CODEC 166 encodes ordecodes voice data. A speech processing routine 168 may perform furtherprocessing of voice data. In further embodiments, the audio CODEC 166and the speech processing routine 118 may be omitted. The varioussoftware routines in the call control system 32 or 36, including thevarious layers 152, 154, 156, and 158 as well as the control tasks 160,CODECs 166, speech processing routine 168, and GUI routine 162, areexecutable on a control unit 170. The control unit 170 is coupled to astorage device 172 in which instructions and data associated with thevarious software routines may be stored.

In the illustrated example arrangement, to provide a voice or audio userinterface to a user sitting at the call control system 32 or 36, aperipheral controller 174 is coupled to a microphone 176 and a speakeror head phone 178 through which a user can talk or listen during a callsession. If the call control system 32 or 36 is not speech-enabled, themicrophone 176 and speaker or head phone 178 may be omitted.

One call control system 32 or 36 may be associated with a correspondingnetwork telephone 30 or 34. Thus, the network telephone 30 or 34 canidentify which device is its controller. Similarly, a call controlsystem 32 or 36 can identify the network telephone it is controlling.The network telephone 30 or 34 includes one or more fields 120 in thestorage device 114 to store an identifier of its call controller, inthis case the call control system 32 or 36. The identifier may be in theform of a network address and port number. For example, an IP addressand a TCP or UDP port may form part of the identifier of the callcontroller 120. Similarly, the call control system 32 or 36 stores oneor more fields 180 in the storage device 172 that stores the identifierof the network telephone it is controlling. Again, the identifier 180may be in the form of a network address and port number, such as an IPaddress and a TCP or UDP port number. The identifier stored in the field120 of the network telephone may be changed by a user to change theassociated call control system. Similarly, the identifier stored in thefield 180 of the call control system may be modified to change thecontrolled network telephone.

In further embodiments, one call control system may be associated withplural network telephones. Also, a single network telephone may beassociated with plural call control systems.

The various control units in the network telephone 30 or 34, the callcontrol 32 or 36, and any other system or device on the data network 11may each include a microprocessor, a microcontroller, a processor card(including one or more microprocessors or controllers), or other controlor computing devices. The storage devices referred to in this discussionmay include one or more machine-readable storage media for storing dataand instructions. The storage media may include different forms ofmemory including semiconductor memory devices such as dynamic or staticrandom access memories (DRAMs or SRAMs), erasable and programmableread-only memories (EPROMs), electrically erasable and programmableread-only memories (EEPROMs) and flash memories; magnetic disks such asfixed, floppy and removable disks; other magnetic media including tape;and optical media such as compact disks (CDs) or digital video disks(DVDs). Instructions that make up the various software routines,modules, or layers in the various network elements may be stored inrespective storage devices. The instructions when executed by arespective control unit cause the corresponding network element toperform programmed acts.

The instructions of the software routines, modules or layers may beloaded or transported to the network element in one of many differentways. For example, code segments including instructions stored on floppydisks, CD or DVD media, a hard disk, or transported through a networkinterface card, modem, or other interface device may be loaded into thesystem and executed as corresponding software routines, modules, orlayers. In the loading or transport process, data signals that areembodied in carrier waves (transmitted over telephone lines, networklines, wireless links, cables, and the like) may communicate the codesegments, including instructions, to the network element. Such carrierwaves may be in the form of electrical, optical, acoustical,electromagnetic, or other types of signals.

Referring to FIG. 4, in accordance with one embodiment, a screen 200that may be provided by the control tasks 160 and graphical userinterface routines 162 in the call control system 32 or 36 isillustrated. The screen 200 as shown in FIG. 4 includes various iconsand items (generally referred to as indicators) to allow a user sittingat the call control system to initiate, terminate, and screen calls overthe data network 11. In the example shown in FIG. 4, the screen 200includes a menu 202, a series of control buttons 204, and a list 206 ofpotential callees. The list 206 provides the first and last names ofpotential callees as well associated electronic mail addresses (or otherinformation such as telephone numbers and so forth). As illustrated inFIG. 4, the name R. Smith may be highlighted in the list 206. Theaddress of R. Smith is displayed in an address field 208. The addressfield 208 may include various formats, such as a PSTN number (e.g.,972-555-1234); a PSTN number and a proxy address (e.g., 972-555-1234@CTEXI300); an IP address (e.g., 47.161.18.72); a SIP address (e.g.,rsmith@nortelnetworks.com); or a SIP address at a specific IP address(e.g., rsmith@47.161.18.72). Identifiers according to other formats maybe illustrated in the address field 208 in further embodiments.

A status field 212 may also be included in the screen 200, which mayshow the status as “not in call,” “outgoing call to R. Smith,” “incomingcall from R. Smith,” and so forth. A plurality of indicators 214 mayalso be provided in the screen 200. A C indicator flashes when anincoming call has been missed. An S indicator gives an indication thatcall screening is active. A P indicator gives an indication that a SIPproxy is in use or not in use. An E indicator gives an indication of thestate of the associated network telephone. Thus, the E indicator is at afirst state if the network telephone is not active and at a second stateif the network telephone is active and available. The E indicator mayalso be at a third state to indicate that a call is currently inprogress.

The screen 200 is also capable of providing a pop-up menu 210 to allow auser to select one or several methods of contacting the desired callee.For example, a first option in the pop-up menu 210 is to call R. Smith.Another option is to send an electronic mail to R. Smith. A third optionis to go to R. Smith's web site.

Other call control operations that may be performed by a user throughthe screen 200 includes volume control, screening of incoming calls,termination of a call session, and other operations.

Referring to FIG. 5, once a call is established with either a caller ora callee, another screen 300 may be shown. A picture of the caller orcallee may be displayed in the screen 300. An icon 304 may be providedto allow the user to hang-up the call, and another icon 306 may beprovided to allow the call to be placed on hold. A status field 308indicates the current status of the call.

Referring to FIG. 6, a message flow between a network telephone, a callcontrol system, and a remote system is illustrated. According to SIP,messages that may be exchanged between network elements include requestsand responses. The remote system may be another call control system, oneof the SIP client systems 38 and 40, the data network-PSTN gateway 20,or any other system capable of establishing a call session on the datanetwork 11. The remote system first sends (at 402) an Invite request(according to SIP) to the call control system. The Invite requestindicates that the receiving node is being invited to participate in asession. The message body of the Invite request contains a description(e.g., in SDP format) of the session to which the receiving node isbeing invited.

The call control system may then send (at 404) a Ringing (SIP) responseback to the remote system. The Ringing response indicates that thecalled user agent has located a possible location where the user hasregistered recently and is trying to alert the user. The call controlsystem may then send (at 406) a Connection_Req message to the networktelephone to initiate a connection between the call control system andthe network telephone. The messaging format between the networktelephone and the call control system may be any predetermined formatthat allows call establishment and control to be performed by the callcontrol system with the network telephone. One such format is theUnified Networks IP Stimulus Protocol, Draft Version 2.1, dated Dec. 7,1999. In further embodiments, other interface protocols may be employed.A description of one embodiment of a protocol for message exchangebetween the network telephone and the call control system is provided inU.S. patent application Ser. No. 09/307,356, entitled “Telephony andData Network Services at a Telephone,” filed on May 7, 1999, which ishereby incorporated by reference.

The Connection_Req message is a generic message which includes one ormore commands that indicates a request to establish a connection. TheConnection_Req message may actually include a ring command to activatethe ringer of the network telephone and other commands to activate thenetwork telephone, such as activation of the handset, headset,microphone, speaker, and so forth. The network telephone may then sendback (at 408) an Ack_Req message to the call control system toacknowledge that the network telephone is available and ready. TheAck_Req message may also be a generic message to acknowledge receipt ofthe Connection_Req message. Upon receipt of Ack_Req message from thenetwork telephone, the call control system sends (at 410) a 200 OK SIPresponse to the remote system to indicate that the request hassucceeded. The remote system then sends (at 412) an Ack request(according to SIP) to the call control system. The Ack request confirmsthat the client has received a final response to an Invite request.

Upon receipt of Ack request, the call control system sends (at 414) aRemote_Answer message to the network telephone to indicate a request toestablish a path for a call session. If accepted, the network telephonethen sends (at 416) an Ack_Answer message back to the call controlsystem. The Remote_Answer message may be a generic message that includesone or more commands to activate the network telephone for call session.One such command is a command to open or connect the audio stream to thehandset, headset, microphone and speaker of the network telephone. Atthat point, a voice path is established (at 418) directly between thenetwork telephone and the remote system. The voice path may be an RTPlink over the data network 11.

To terminate the call, the remote system may issue (at 420) a Byerequest to the call control system. The call control system thenresponds (at 422) with a 200 OK, indicating that the call has beenterminated. Then, the call control system sends (at 424) aDisconnect_Req message to the network telephone to disconnect thenetwork telephone from the data network. The Disconnect_Req message be ageneric message including one or more commands to deactivate variouscomponents of the network telephone. For example, the audio stream maybe closed or disconnected, and the handset, headset, microphone, andspeaker may be deactivated. The network telephone then returns (at 426)an Ack_Disconnect message back to the call control system to indicatethat the call has been disconnected.

Referring to FIG. 7, an outgoing call message flow is illustrated. Inthe illustrated example, the user can initiate the call from the callcontrol system. However, the user can also make the external call fromthe network telephone by entering the desired number in appropriatebuttons of the network telephone. In that case, messages are exchangedbetween the network telephone and the call control system initially toindicate to the call control system that the user has started a phonecall from the network telephone.

To start the call session, the call control system sends (at 502) anInvite request to the remote system. The remote system then sends back(at 504) a Ringing response. In response, the call control system sends(at 506) a Remote_Alerting message to the network telephone indicatingthat the call has been placed. The network telephone then returns (at508) an Ack_Alerting message. At some point, the remote system, once ithas answered the call, issues (at 510) a 200 OK message to the callcontrol system. In response, the call control system then sends (at 512)an Ack request back to the remote system. The call control system alsosends (at 514) a Remote_Answer message to the network telephone, whichreturns (at 516) an Ack_Answer message to the call control system. Atthat point, a voice path (e.g., an RTP path) is established (at 518)between the network telephone and the remote system over the datanetwork 11.

To terminate the call, the remote system may issue (at 520) a Byerequest. In response, the call control system may terminate the call bysending (at 522) a 200 OK message. The call control system then sends(at 524) a Disconnect_Req message to the network telephone, whichreturns (at 526) an Ack_Disconnect message to the call control system.At this point, the RTP voice path is terminated.

While the invention has been disclosed with respect to a limited numberof embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of the invention.

1. A method of communicating over a data network, comprising: providinga user interface in a control system for establishing a call session inwhich audio and video data are communicated; communicating, by thecontrol system, one or more control messages over the data network toestablish a call session with a remote device in response to receipt ofa request through the user interface; and transmitting one or morecommands to a telephony device connected to the data network andassociated with the control system to establish the call session betweenthe telephony device and the remote device over the data network toexchange the audio data and video data between the telephony device andthe remote device.
 2. The method of claim 1, wherein the communicatedone or more control messages and the transmitted one or more commandsare according to different formats.
 3. The method of claim 1, whereinestablishing the call session includes establishing a Real-Time Protocolsession over the data network.
 4. The method of claim 1, whereincommunicating the one or more control messages includes communicatingmessages according to a protocol defining real-time, interactive callsessions over a packet-switched data network.
 5. The method of claim 1,wherein communicating the one or more control messages includescommunicating one or more Session Initiation Protocol messages.
 6. Themethod of claim 1, further comprising storing, in the control system, anInternet Protocol address and port of the telephony device.
 7. Themethod of claim 1, further comprising receiving an indication from thetelephony device to establish another call session with the remotedevice.
 8. The method of claim 1, further comprising displayinggraphical user interface information of the call session on the controlsystem.
 9. The method of claim 1, further comprising terminating thecall session using either the user interface or the telephony device.10. The method of claim 1, further comprising displaying an image of atleast one of a caller or callee in the user interface.
 11. A method ofcommunicating over a data network, comprising: in a control system,communicating one or more control messages over the data network toestablish a call session with a remote device coupled to the datanetwork, wherein audio and video data are exchanged in the call session;transmitting one or more commands to a network telephone coupled to thedata network; establishing the call session between the networktelephone and the remote device over the data network to exchange audioand video data; and displaying information associated with the callsession on the control system.
 12. The method of claim 11, whereindisplaying the information includes displaying graphical user interfaceinformation.
 13. The method of claim 11, wherein communicating the oneor more control messages includes communicating Session InitiationProtocol messages.
 14. The method of claim 11, further comprisingproviding one or more indicators for call control in the control system.15. A system for controlling a user terminal connected to a datanetwork, comprising: a user interface including one or more selectorsfor call control relating to call sessions; a controller adapted toreceive a request from the user interface and to generate one or moremessages for communication over the data network to establish a callsession with a remote device; and an interface to transmit one or morecommands relating to the call session to the user terminal to establisha link between the user terminal and the remote device over the datanetwork, wherein audio and video data are exchanged in the link.
 16. Thesystem of claim 15, wherein the one or more messages include SessionInitiation Protocol messages.
 17. The system of claim 15, wherein theuser interface includes one or more elements to display informationrelating to the call session.
 18. The system of claim 15, wherein theinformation displayable in the user interface includes an image of atleast one of a caller and callee.
 19. An article including one or moremachine-readable storage media containing instructions for controllingmultimedia communications over a data network, the instructions whenexecuted causing a system to: provide a user interface in the system todisplay information associated with a call session; communicate one ormore control messages over the data network with a remote device toestablish the call session between a user terminal and the remotedevice, wherein multimedia data, including audio and video data, isexchanged in the call session; and control the user terminal during thecall session.
 20. The article of claim 19, wherein the one or morestorage media contain instructions that when executed cause the systemto communicate Session Initiation Protocol messages.